1. Field of the Invention
This invention relates to memory cells, and in particular to a bit line powered static bipolar random access memory cell.
2. Description of the Prior Art
The application of the translinear principle to digital integrated circuits was first proposed by E. Seevinck in IEEE Journal of Solid State Circuits, Volume SC-13, No. 4, Aug. 19, 1978 at pages 528-530. In that paper Seevinck uses diodes as loads for a random access memory cell. The potential drop thereby created, however, is so large as to require a below ground power supply on the commonly coupled emitters of the RAM cell. This requirement made it difficult to utilize Seevinck's cell in conjunction with conventionally available power supplies.
The operation of translinear memory cells has also been discussed in J. Lohstroh, "Static Bipolar RAM Cell with Compact Punch-Through Loads," Digest of Technical Papers, 1979 International Solid State Circuit Conference, February 1979, pages 14-15. In that reference and in the Seevinck paper mentioned above, the principles of operation of the translinear memory cell are discussed. In a translinear memory cell a regenerative circuit with cross coupled transistors using diodes as loads is possible if the ideality factor of the diode is greater than one. The ideality factor of a diode is defined by n where: ##EQU1## Where I.sub.D is the current through the diode, I.sub.s is the saturation current, e is the base of natural logarithms, q is the charge on an electron, V.sub.D is the voltage across the diode, K is Boltzman's constant, and T is the absolute temperature.
I, in may U.S. Pat. No. 4,032,902 issued June 28, 1977, and entitled "Semiconductor Memory Cell Circuit and Structure," teach the fabrication and operation of a bit line powered integrated circuit memory cell structure.